$(document).ready(function() {		
	//change the main div to overflow-hidden as we can use the slider now
	$('#scroll-pane').css('overflow','hidden');

	//compare the height of the scroll content to the scroll pane to see if we need a scrollbar
	var difference = $('#scroll-content').height()-$('#scroll-pane').height();//eg it's 200px longer 

	if(difference>0)//if the scrollbar is needed, set it up...
	{
	   var proportion = difference / $('#scroll-content').height();//eg 200px/500px
	   var handleHeight = Math.round((1-proportion)*$('#scroll-pane').height());//set the proportional height - round it to make sure everything adds up correctly later on
	   handleHeight -= handleHeight%2; 

	   $("#scroll-pane").after('<\div id="slider-wrap"><\div id="slider-vertical"><\/div><\/div>');//append the necessary divs so they're only there if needed
	   $("#slider-wrap").height($("#scroll-pane").height());//set the height of the slider bar to that of the scroll pane


	   //set up the slider 
	   $('#slider-vertical').slider({
	      orientation: 'vertical',
	      min: 0,
	      max: 100,
	      value: 100,
	      slide: function(event, ui) {//used so the content scrolls when the slider is dragged
	         var topValue = -((100-ui.value)*difference/100);
	         $('#scroll-content').css({top:topValue});//move the top up (negative value) by the percentage the slider has been moved times the difference in height
	      },
	      change: function(event, ui) {//used so the content scrolls when the slider is changed by a click outside the handle or by the mousewheel
	         var topValue = -((100-ui.value)*difference/100);
	         $('#scroll-content').css({top:topValue});//move the top up (negative value) by the percentage the slider has been moved times the difference in height
	      }
	   });

	   //set the handle height and bottom margin so the middle of the handle is in line with the slider
	   $(".ui-slider-handle").css({height:handleHeight,'margin-bottom':-0.5*handleHeight});
		
	   var origSliderHeight = $("#slider-vertical").height();//read the original slider height
	   var sliderHeight = origSliderHeight - handleHeight ;//the height through which the handle can move needs to be the original height minus the handle height
	   var sliderMargin =  (origSliderHeight - sliderHeight)*0.5;//so the slider needs to have both top and bottom margins equal to half the difference
	   $(".ui-slider").css({height:sliderHeight,'margin-top':sliderMargin});//set the slider height and margins
	   
	   //create elements to hold the images for the scrollbar handle
	   $(".ui-slider-handle").append('<img id="scrollbar-top" src="../images/scrollbar-handle-top.png"/>');
	   $(".ui-slider-handle").append('<img id="scrollbar-bottom" src="../images/scrollbar-handle-bottom.png"/>');
	   $(".ui-slider-handle").append('<img id="scrollbar-grip" src="../images/scrollbar-handle-grip.png"/>');
	}//end if

	$(".ui-slider").click(function(event){//stop any clicks on the slider propagating through to the code below
	   	event.stopPropagation();
	   });
	   
	$("#slider-wrap").click(function(event){//clicks on the wrap outside the slider range
		  var offsetTop = $(this).offset().top;//read the offset of the scroll pane
		  var clickValue = (event.pageY-offsetTop)*100/$(this).height();//find the click point, subtract the offset, and calculate percentage of the slider clicked
		  $("#slider-vertical").slider("value", 100-clickValue);//set the new value of the slider
	}); 
		 
	//additional code for mousewheel
	$("#scroll-pane,#slider-wrap").mousewheel(function(event, delta){
		var speed = 5;
		var sliderVal = $("#slider-vertical").slider("value");//read current value of the slider
		
		sliderVal += (delta*speed);//increment the current value

		$("#slider-vertical").slider("value", sliderVal);//and set the new value of the slider
		
		event.preventDefault();//stop any default behaviour
	});
});